1,2,3‐Triazol‐1,4‐diyl‐Fluoroionophores for Zn²⁺, Mg²⁺ and Ca²⁺ based on Fluorescence Intensity Enhancements in Water

Abstract

Herein, we represent cation‐responsive fluorescent probes for the divalent cations Zn2+, Mg2+ and Ca2+, which show cation‐induced fluorescence enhancements (FE) in water. The Zn2+‐responsive probes Zn1, Zn2, Zn3 and Zn4 are based on o‐aminoanisole‐N,N‐diacetic acid (AADA) derivatives and show in the presence of Zn2+ FE factors of 11.4, 13.9, 6.1 and 8.2, respectively. Most of all, Zn1 and Zn2 show higher Zn2+ induced FE than the regioisomeric triazole linked fluorescent probes Zn3 and Zn4, respectively. In this set, ZN2 is the most suitable probe to detect extracellular Zn2+ levels. For the Mg2+‐responsive fluorescent probes Mg1, Mg2 and Mg3 based on o‐aminophenol‐N,N,O‐triacetic acid (APTRA) derivatives, we also found that the regioisomeric linkage influences the fluorescence responds towards Mg2+ (Mg1+100 mM Mg2+ (FEF=13.2) and Mg3+100 mM Mg2+ (FEF=2.1)). Mg2 shows the highest Mg2+‐induced FE by a factor of 25.7 and an appropriate Kd value of 3 mM to measure intracellular Mg2+ levels. Further, the Ca2+‐responsive fluorescent probes Ca1 and Ca2 equipped with a 1,2‐bis(o‐aminophenoxy)ethane‐N,N,N’,N’‐tetraacetic acid (BAPTA) derivative show high Ca2+‐induced FEs (Ca1 (FEF=22.1) and Ca2 (FEF=23.0)). Herein, only Ca1 (Kd=313 nM) is a suitable Ca2+ fluorescent indicator to determine intracellular Ca2+ levels.